There are drug and surgical treatments to decrease intraocular pressure. When therapy and surgery do not work, implants are used (in the form of bypasses known in the field as ‘shunts’) with passive valves that drain the intraocular liquid (aqueous humor) to the outside through tubes and plates. See, for example, Lim, K. S., ‘Glaucoma drainage devices, past, present and future’, Br. J. Ophtalmol (1968), 82:1083-1089 or the international patent (PCT) WO99/66871, which describes a device—of about 1 mm long—implantable in the eye to decrease ocular pressure by a stopper that regulates pressure, that releases when an optimal value is exceeded to drain the liquid that is absorbed by the surrounding tissues. However, said implants have shown so far some drawbacks, such as:                the implant size is not small enough (lower than 1 cm) nor material are adequate to avoid fibrosis (see, Lim et al, Glaucoma drainage devices; past, present and future), Br J Ophthalmol 1998; 82:1083-1089)        Surgery is not able to optimize or turn intraocular pressure predictable, resulting in hypotony or high resistance to flow (see, Q H. Nguyen, ‘Avoiding and managing complications of glaucoma drainage implants’, Curr Opin Ophthalmol 15:147-150, 2004)        Intraocular pressure varies during the day, a variation that can not be compensated by passive valves (see, Kitazawa Y, Horie T. ‘Diurnal variation of intraocular pressure in primary open-angle glaucoma’, Am J Ophthalmol, 1975; 79:557-566)        There is obstruction by particles (proteins or cells) due to hydrophobicity of the silicon used to make the implant. See, ‘A Compact Chemical-Resistant Microvalve Array Using Parylene Membrane and Pneumatic Actuation’, Z Hua, O Srivannavit, Y Xia, E Gulari—MEMS, NANO and Smart Systems, 2004. ICMENS 2004. Proceedings . . . , 2004—ieeexplore.ieee.org.        
There have been attempts to replace said passive valves by electrochemical or electromagnetic actuating microvalves using MEMS technology. To this respect, reference can be made to the article of Byunghoon B., ‘In vitro experiment of the pressure regulating valve for a glaucoma implant’, J. Micromech. Microeng. (2003), 13:613-619, wherein an ocular implant to decrease glaucoma by an electromagnetic valve opening or closing mechanism and a permanent magnet moved by the magnetic force deforming the membrane is shown. The membrane is made of a deformable polymer of low elasticity module (Young module). Also, the U.S. Pat. No. 6,168,575 issued to Soltanpour et al, entitled ‘Method and apparatus for controlling intraocular pressure’, describes a small pump of 5 to 15 mm of length which is implanted in the eye to remove the excess of fluid that can be adjusted manually or automatically. Control is made by a pressure sensor connected to a microprocessor, being the sensor disposed externally to the eye. Said US Patent discusses the drawbacks of the automatic adjustment as to the complications related to muscular hypotony.
U.S. Pat. No. 6,589,203 describes an ocular implantable device having a deformable surface made of a material capable of supporting continuous deformations and a drainage tube that has a valve sensible to pressure variations that limits the flow by the tube. Most recent reference is U.S. Pat. No. 6,682,500 issued to Soltanpour et al, entitled ‘Synthetic muscle-based diaphragm pump apparatuses’ that describes a device with a diaphragm pump made of a synthetic polymer of a metal compound and includes a pressure sensor. This apparatus is equipped with two valves, one in the inlet conduit to the pump and the other in the outlet conduit, to regulate the flow of fluid in the pump. This reference also allows implementing an inductive coupling to transfer signals between the implant and an external accessory.
Unfortunately, the abovementioned implants have biocompatibility and size problems as the previous ones that do not allow meeting design requirements. Problems such as malfunctioning and obstruction have not been addressed by said patents.
Less relevant references but that could be also of interest in the field are the French Patent 2.553.658 (valve implant to cure glaucoma) and the U.S. Pat. Nos. 4,282,882 (apparatus to modify intraocular pressure), 4,402,681 (implantable artificial valve to regulate intraocular pressure), 4,585,457 (inflatable intraocular lens), 4,886,488 (glaucoma lachrymal drainage system and method), 5,041,081 (ocular implant to control glaucoma), 5,127,901 (implant with sub-conjuntival arc), 5,433,701 (apparatus to reduce ocular pressure), 5,454,796 (device and method to control intraocular fluid pressure), 5,520,631; 5,704,907 and 6,102,045 (methods and apparatuses to decrease intraocular pressure), 5,523,808 (ophthalmic apparatus provided with a measuring system of the intraocular pressure), 5,626,559 (ophthalmic device to drain excess intraocular fluid), 5,651,782 (method and apparatus to implant a mesh in glaucoma surgery), 5,656,026 (in vitro assay method of a valve unidirectional gradient limiting device to drain glaucoma), 5,713,844 (device and method to regulate intraocular pressure), 5,743,868 (cornea implantable device to regulate pressure), 5,785,674 (device and method for treating glaucoma), 5,807,302 (treatment of glaucoma), 5,868,697 (intraocular implant), 5,968,058 (device and method to implant an intraocular implant), 6,077,299 (non-invasive implant with adjustable valve to drain aqueous humor in glaucoma), 6,083,161 (apparatus and method for improving establish ocular pressure), 6,113,342 (diagnosis method and apparatus for providing the effective intraocular pressure based in cornea measurements), 6,142,990 (medical apparatus, specially to reduce intraocular pressure), 6,464,724 (stent device and method for treating glaucoma), 6,468,283 (method for regulating pressure with an ocular implant), 6,510,600 (method for manufacturing a flow regulating implant), 6,558,342 and 6,726,664 (flow control devices, introducers, and methods of implanting), 6,638,239 (apparatus and method for treating glaucoma) and 6,730,056 (eye implant for treating glaucoma and method for manufacturing the same).